1. Field of the Invention
The present invention relates to a fore-and-aft adjusting device for a head rest used in an automotive seat, which is adapted for adjusting the positions of the head rest forwardly and backwardly relative to the seat, using a friction means.
2. Description of the Prior Art
The hitherto conventional fore-and-aft adjusting devices of this kind for a head rest using a friction means included either a metallic friction means such as a plate spring (as known from the Japanese Utility Model Publication No. 60-36111) or a synthetic resin friction means, for instance.
Those prior art devices have attendent respective drawbacks and disadvantages. In the former device, the metallic friction means is in contact with the head rest frame in a small contact area, resulting in insufficient friction effects, whereas in the latter one, although having a sufficient contact area between the friction means and head rest frame and thus being free from this drawback, the synthetic resin nature of the friction means creates the possibility of its deformation due to frictional heat between the frame and friction means, which gives an undesired variation to its friction effect.